“Matter, though divisible in an extreme degree, is nevertheless not infinitely divisible. That is, there must be some point beyond which we cannot go in the division of matter. … I have chosen the word “atom” to signify these ultimate particles.”
— John Dalton
Today is the 250th anniversary of the birth of English chemist John Dalton, who was an early pioneer in what became modern atomic theory. His career was quite varied. He and his brother were both red-green color blind, which led him to theorize that the condition was hereditary, which was later proven to be true. His study of meteorology, and particularly of atmospheric pressure led to a further study of gasses led to Dalton’s Law of Partial Pressures, which has a few practical applications – notably for divers in calculating the effect of differring pressures as depth changes on the oxygen/nitrogen in their tanks. This ongoing study of gasses is ultimately what led him to the conclusion that all matter was composed of particles, which he labeled atoms (from the Greek atomos). In 1803 he created the first table of atomic weights.
Featured image, which I liked a great deal because it covered so much in one image, has been borrowed from https://learnodo-newtonic.com/john-dalton-contribution